John Marston was born in 1873. His father was an illiterate Scottish immigrant who was born on the boat to New York, while his mother was a prostitute, who died during John's birth. John initially lived with his father, a man who loved Scotland and always talked about it. However, he was blinded in a bar fight south of Chicago and died at some point later, when John was eight years old. The circumstances around his death are unknown, although John was told that he died in the bar fight.

John was subsequently sent to an orphanage, where he spent the next few years. He eventually ran away and tried to make his own luck living out in the streets. At the age of 11, John committed his first murder when he shot a man, although he claimed it was not his fault. In 1885, at the age of 12, Marston had been caught stealing by homesteaders in Illinois, who planned on hanging him. Dutch van der Linde stepped in and saved the young boy, taking him under his wing; John was thus inducted into the Van der Linde gang, alongside Hosea Matthews, Arthur Morgan, and Susan Grimshaw. The gang became a surrogate family to the young boy, with Dutch becoming his mentor and father figure. He taught John how to read, shoot, hunt, gather, and instilled him with a love of nature and things other than power.

John developed into an experienced outlaw, running with Dutch, Hosea, Bill Williamson, Arthur Morgan, Javier Escuella and several others, committing robberies, raids, murders, kidnappings and other crimes across the American frontier. Alongside Morgan, Marston was viewed as Dutch's proudest protégé; many members of the gang considered John to be Dutch's favorite and "golden boy", much to the envy of certain people, such as Bill. Marston had fallen under the sway of Dutch's philosophy, believing that the gang stole and fought for a reason. In stealing from the rich, they, in turn, gave to the poor. They wanted to elicit change in the people of the West, although he later came to admit that these were excuses to let them rob and steal indiscriminately.

In 1894, a prostitute named Abigail Roberts joined the gang. Despite having sexual relations with most of the gang members, she eventually fell in love with John. They later had a son together in 1895, whom they named Jack. The gang became an extended family to Jack, with most of the members becoming aunts and uncles to him. In his early years, John had a lot of difficulties connecting with his son due to doubts as to whether or not he was Jack's biological father, as well as fears about his own ability to raise him. Around 1896, John left the gang for a year. His return was met well with Dutch and certain other members of the gang, whilst Arthur felt betrayed by his actions. A rift between the two steadily grew over the next few years.

The gang picked up new members such as Micah Bell, Lenny Summers, and Charles Smith as they traversed the Grizzlies circa 1898. They continued moving east until they reached the up-and-coming port town of Blackwater, where they decided to stay for a while. Here, Micah ended up encouraging Dutch to pursue a boat heist, which John participated in alongside Javier, Sean, and the Callander brothers - Mac and Davey. The heist went wrong when Dutch shot a defenseless young woman named Heidi McCourt in the head and a unit of Pinkerton agents ambushed the gang, resulting in an eruption of violence. The gang escaped and managed to stash the money from the boat somewhere in Blackwater. The heist was a disaster, leading to the deaths of Davey and Jenny Kirk, Mac being separated, and Sean's capture by bounty hunters. John took a bullet in the arm and escaped with the rest of the gang, heading north towards Big Valley.

John Marston 1873'te doğdu. Babası Amerika'ya göç eden bir İskoç, annesi doğum sırasında ölen bir fahişeydi. John'a göre, babası muhtemelen annesinin aynı zamanda pezevengiydi. John'un babası, John 8 yaşındayken 1881'de öldü.

John daha sonraki birkaç yılını geçireceği bir yetimhaneye gönderildi. Oradan kaçtı ve hayatını sokaklarda kazanmaya çalıştı. John, 11 yaşında, bir adamı vurduğunda ilk cinayetini işledi, ancak bunu kasıtlı yapmadığını iddia etti. 1885'te 12 yaşındayken Marston, onu asmak isteyen Illinois'deki çiftlik sahipleri tarafından hırsızlık yaparken yakalandı. Dutch van der Linde araya girdi ve genç John'u kanatlarının altına alarak kurtardı; John böylece Hosea Matthews, Arthur Morgan ve Susan Grimshaw ile birlikte Van der Linde çetesine katılmış oldu.

Çete, genç John'un ebeveynleri olan bir aile haline geldi ve Dutch onun için akıl hocası ve baba figürü oldu. John'a okumayı, ateş etmeyi, avlanmayı öğretti ve ona doğa sevgisini aşıladı. John, Dutch, Hosea, Bill Williamson, Arthur Morgan, Javier Escuella ve diğer birkaç kişiyle birlikte, Amerikan sınırında soygunlar, baskınlar, cinayetler, adam kaçırma ve diğer suçları işleyen deneyimli bir kanun kaçağı haline geldi. Morgan'ın yanı sıra Marston, Dutch'ın en öz verili oğullarından biri olarak görülüyordu; Çetenin birçok üyesi John'u Dutch'ın favorisi ve "altın çocuğu" olarak görüyordu, Bill gibi bazı üyeler ise bu durum karşısında kıskançlık duymaktaydı.

1894'te Abigail Roberts adında bir fahişe çeteye katıldı. Çete üyelerinin çoğuyla cinsel ilişkiye girmesine rağmen Abigail, John'a aşık oldu. Daha sonra 1895'te Jack adını verdikleri bir oğulları oldu. Çete, Jack'in büyük bir ailesi haline geldi ve üyelerin çoğu onun için teyze ve amca figürü oldu. John, ilk yıllarında, Jack'in biyolojik babası olup olmadığına dair şüpheler içindeydi ve bu nedenden dolayı onunla bağlantı kurmakta zorluk yaşadı. 1896 civarında John, çeteden bir yıllığına ayrıldı. Dönüşü Dutch ve çetenin diğer bazı üyeleri tarafından iyi karşılanırken, Arthur, John'un bu hareketi nedeniyle ihanete uğradığını hissetti. Önlerindeki birkaç yıl ikili arasında gerginlik oluştu.